JP2841377B2 - Phase difference plate - Google Patents

Description

The present invention relates to a retardation plate applicable to a liquid crystal display device and the like.

[Conventional technology]

The retardation plate is a film or sheet having birefringence. Since the light transmitted through the phase difference plate has different refractive indices in two directions orthogonal to each other, a phase difference occurs between the orthogonal light after transmission.

As a retardation plate, there is a so-called 板 λ plate having a function of generating a 差 λ phase difference with respect to the wavelength λ of an incident light beam, which is currently commercially available and practically used. This 1 / 4λ plate is obtained by stretching a cellulose acetate film in a uniaxial direction. The 1 / 4λ plate becomes a circular polarizer when bonded at an angle of 45 degrees to the optical axis of the linear polarizer, and has an anti-glare function that cuts reflected light. Used in materials.

As the polymer material constituting the 1 / 4λ plate, in addition to the above-mentioned cellulose resin, a vinyl chloride resin (Japanese Patent Publication No.
JP-A-34477, JP-A-56-125702, etc.), polycarbonate-based resin (JP-B-41-12190, JP-A-56-125702)
-130703), acrylonitrile-based resins (JP-A
No. 56-130702), styrene resins (Japanese Patent Application Laid-Open No.
No. 5703), polyolefin-based resin (JP-A-60-2450)
No. 2) have been proposed, but all are so-called 1 / 4λ plates having a measured retardation of around 135 nm. The retardation value (R value) is the product of the thickness d of the film or sheet and the birefringence △ n of the film,
That is, R = △ n × d.

On the other hand, as described in JP-A-61-186937 and JP-A-60-26322, the twist angle of liquid crystal molecules is 90%.
A liquid crystal display device in which a pair of polarizing plates are arranged above and below a liquid crystal cell so that their absorption axes are orthogonal or parallel (generally referred to as a TN type liquid crystal display, which has been applied to watches, calculators, etc.) Attempts have also been made to improve the display quality by applying a retardation plate to the optical disk.

Furthermore, in recent years, with the increase in display capacity and the demand for enlargement of the display screen, the twist angle of liquid crystal molecules is 90 degrees or more, that is,
A liquid crystal display device having an angle of about 180 to 270 degrees has been developed (generally referred to as an STN type liquid crystal display device). But conventional T
In the STN-type liquid crystal display device, coloring caused by birefringence of liquid crystal molecules occurs, and black-and-white display cannot be performed in the STN-type liquid crystal display device. For example, the background color is yellow-green, and the display color is dark blue. If the display device has such a hue, there are many restrictions when performing color display such as multi-color and full-color.To solve this problem, for example, Nikkei Micro Device, October 1987 As described on page 84, a polarizing plate
There is disclosed a method of adding another achromatizing liquid crystal cell as an optical compensator to an STN type liquid crystal cell to solve coloring and to enable monochrome display.

[Problems to be solved by the invention]

The method of adding another achromatizing liquid crystal cell to the STN-type liquid crystal cell as an optical compensator eliminates coloring and enables monochrome display, but (1) is expensive and inferior in economy.
There are problems such as (2) heavy and (3) thick, and in addition to the improvement of the display performance described above, it is required to solve these problems together.

Although it is possible in principle to use a retardation plate instead of the achromatizing liquid crystal cell, a conventional 1 / 4λ plate (1) does not optically match the retardation value.
(2) The optical axis is not constant. (3) Uniform black and white display with large optical color unevenness is not achieved. For this reason, it cannot be applied to new uses such as the liquid crystal display device described above.

[Means for solving the problem]

The present invention has been completed as a result of repeated studies in view of the above points, and is as follows.

That is, the present invention is a film or sheet formed by uniaxially stretching a thermoplastic polymer film or sheet, the retardation value is in the range of 30 to 1200 nm, and the deflection width of the retardation is 10% or less. The present invention relates to a retardation plate characterized by having a change rate of 1.3% / cm or less and a composite polarizing plate obtained by laminating the retardation plate on a polarizing plate.

The retardation plate of the present invention relates to a novel retardation plate having an appropriate retardation value and having little optical unevenness in color. The retardation value is in the range of 30 to 1200 nm, but is preferably adjusted to the range of 200 to 1000 nm. A more appropriate retardation value is selected depending on the specific application. For example, retardation values in the range of 200 to 350 nm and in the range of 475 to 625 nm can be exemplified for liquid crystal display devices.

Further, in the present invention, the amplitude (ΔR) of the retardation value of the retardation plate is 10% or less, preferably 7% or less, more preferably 5% or less, and its change rate (G ) Is controlled to 1.3% / cm or less, preferably 1.0% / cm or less, and more preferably 0.6% / cm or less, whereby an excellent retardation plate free from optical color unevenness can be obtained. .

Further, in order to obtain a retardation plate having no optical color unevenness as described above, it is preferable that the thickness accuracy of the heat-soluble polymer film or sheet to be used is as uniform as possible. The swing width (振 x) of (x) is 0.1x or less, preferably 0.07x or less, more preferably 0.05x or less, and the rate of change (G ') is 0.015x / cm or less, preferably 0.012x or less. By using an original film or sheet having a thickness of not more than x / cm, more preferably not more than 0.007x / cm, an excellent retardation plate having no color unevenness can be obtained.

If the thermoplastic resin used in the retardation plate of the present invention is exemplified, polycarbonate resin, polymethyl methacrylate, methyl methacrylate obtained by copolymerizing other ethylene-based comonomer with methyl methacrylate as a main component. Poly (meth) acrylate resins such as copolymers, polystyrene resins such as styrene copolymers obtained by copolymerizing polystyrene, styrene as a main component and other ethylene comonomer, polyacrylonitrile, acrylonitrile copolymer, etc. Acrylonitrile resin, polyethylene terephthalate, polyester resin such as polyester copolymer, polyamide resin such as nylon 6, nylon 66, polyvinyl chloride, polychlorinated resin such as vinyl chloride copolymer, polyethylene, polypropylene, ethylene Copolymer, propylene Polyolefin-based resins such as copolymers, polysulfone, polyethersulfone, fluorine-based resins, etc. and modified products thereof, and transparent low-molecular compounds or transparent inorganic compounds such as high-molecular liquid crystals or low-molecular liquid crystals in these resins And at least one resin material selected from blends of the above.

Among them, preferred resins include polycarbonate resins, polyethylene terephthalate, polyester resins such as polyester copolymers, polysulfone, polyvinyl chloride, polyvinyl chloride resins such as vinyl chloride copolymers, and acrylonitrile resins. Can be.

A method of using the above-mentioned thermoplastic polymer compound as a retardation plate will be described below. The retardation plate of the present invention is formed into a raw film or sheet by a known film forming method of the thermoplastic polymer by a known film forming method, that is, a solvent casting method, a calendering method, or an extrusion method, and then appropriately stretched in a uniaxial direction. It is manufactured by doing.

The optical axis is constant, and in order to obtain a retardation plate with less optical color unevenness, the original film or sheet has a good thickness accuracy and is as optically homogeneous as possible,
It is required that the deflection width (Δx) of the thickness (x) is 0.1x or less and the thickness change rate (G ′) is 0.015x / cm or less. The thickness (x) of the raw film or sheet is 30cm x 30
cm sample was taken and measured equally at 36 locations
The average value of 86 points, the thickness fluctuation (Δx) is the difference between the maximum value and the minimum value of the 36 points, and the thickness change rate (G ′) is the difference between adjacent measurement points. The largest value among the values divided by the point interval (distance).

Also, it is not preferable that a die line or the like is generated at the time of forming the raw film or sheet. Usually, when a film or a sheet is formed, fine orientation is often generated, and it is also a preferable method to reduce the fine orientation before stretching. Heat treatment is effective as a method for reducing micro-orientation before stretching.

In order to produce the retardation film of the present invention, the film or sheet is subjected to a heat treatment at a temperature not lower than the heat deformation temperature before stretching.

When the heat treatment is performed, the birefringence of the raw film or sheet becomes substantially zero, and a substantially perfect non-oriented film or sheet is obtained.

As a method for uniaxially stretching the thus obtained raw film or sheet, known methods include a transverse uniaxial stretching method by a tenter method, a compression stretching method between rolls, and a vertical uniaxial stretching method using rolls having different peripheral speeds. Can be adopted.

In the present invention, in order to obtain a retardation plate having a small fluctuation width of the retardation value and a small change rate thereof, a neck-in rate (100 × 100) defined from the film width A before stretching and the film width B after stretching. (AB) / A) must be suppressed to 10% or less, preferably 5% or less, and more preferably substantially zero. Accordingly, the most effective stretching method in the present invention is the transverse uniaxial stretching direction by the tenter method which does not substantially cause neck-in.

The transverse uniaxial stretching by the tenter method generally includes three steps of a preheating step, a stretching step, and a heat treatment step. The preheating step is useful because it has the same role as the heat treatment step of making the birefringence of the film or sheet substantially zero. The stretching step is the most important step for forming a retardation plate. Depending on the type of thermoplastic resin used, the thickness, the necessary retardation value, etc., the processing conditions are different, but the optically non-uniform retardation of the present invention is small. In order to obtain a plate, it is important to perform uniform stretching, and for that, it is particularly essential to select a stretching temperature under appropriate conditions.

The stretching temperature needs to be higher than the temperature at which the apparent yield point disappears in the stress-strain curve of the tensile test. If the stretching temperature is in a temperature range where the yield point appears in the stress-strain curve or lower, the stretching is not uniform, the thickness of the stretched product becomes uneven, and the deflection width and change rate of the retardation increase.

The stretching ratio is not particularly limited, and varies depending on the type of the thermoplastic resin used, but is preferably about 1.2 to 6 times, preferably 1.2 times.
It is about 4.0 times.

The heat treatment step after stretching is a useful step for improving the dimensional stability of the obtained stretched film or sheet, and improving the uniformity of the retardation, and the heat treatment temperature is from the stretching temperature or lower to around the heating deformation temperature. preferable.

The heating deformation temperature refers to a value measured at JIS K6735 18.6 kg f / cm ² .

The retardation in the present invention can be measured by a polarizing microscope, a spectrophotometer or the like, and the average value of the retardation () is 30 cm × 30 mm from the stretched film or sheet.
cm sample was taken and measured equally at 36 locations
Expressed as the average value of 36 points, the amplitude of retardation (シ ョ ン
R) is a value obtained by dividing the difference between the maximum value and the minimum value of the 36 points by an average value (expressed as a percentage), or the rate of change in retardation (G) is the average value of the difference between the measurement values of adjacent measurement points. Means the largest value among the values obtained by dividing the value (expressed as a percentage) by the measurement point interval (distance).

If the fluctuation width ΔR is 10% or more or G is 1.3% / cm or more, it cannot be used for various optical applications, especially for liquid crystal display devices due to optical unevenness.

The retardation plate of the present invention can also be applied to a liquid crystal display device or the like by bonding it to one surface of a polarizing plate to form a composite polarizing plate.

As the polarizing plate constituting the composite polarizing plate of the present invention, any polarizing plate can be used. As an example, a film made of polyvinyl alcohol or a derivative thereof is uniaxially stretched and oriented, and after adsorbing iodine or a dichroic dye as a polarizing element, a non-rotatory cellulose acetate film such as triacetic acid or cellulose is used. On both sides. Furthermore, a dichroic dye was blended with a hydrophobic resin such as a polyene-based polarizing plate or polyethylene terephthalate obtained by dehydrochlorination of a polyvinyl chloride film or dehydration treatment of a polyvinyl alcohol-based film, and uniaxially oriented. A polarizing plate of a type can be used. Above all, a polyvinyl alcohol film, adsorbing iodine or a dichroic dye, and a uniaxially-aligned polarizer and a cellulose-based film such as cellulose triacetate bonded on both sides as a protective film have polarizing properties. It is preferable from the viewpoint of hue characteristics.

The retardation plate of the present invention, and, using the polarizing plate, to form the composite polarizing plate of the present invention the optical axis of the polarizing plate and the optical axis of the retardation plate 15 to 75 degrees, preferably 30 to 60 degrees, More preferably, it is achieved by bonding using an adhesive or an adhesive in the range of 40 to 50 degrees.

Further, the protective film on one side of the linear polarizing plate is removed, and the retardation plate is directly adhered to the polarizer using an adhesive or an adhesive. One side of a linear polarizing plate composed of a combination of chromatic dyes, a configuration in which a retardation plate is adhered using an adhesive, or an adhesive or the like is also included in the scope of the composite polarizing plate of the present invention. .

〔The invention's effect〕

The retardation plate or composite polarizing plate obtained in this way has good optical performance and at the same time 80 ° C and 60 ° C.
Since it can pass the durability promotion test at × 90% RH, it can be used for new uses such as a liquid crystal display.

 An example in which the present invention is applied to a liquid crystal display is shown below.

(1) If a retardation plate is placed above the upper polarizing plate of a TN type liquid crystal display device in which the twist angle of liquid crystal molecules is 90 degrees, there is no rainbow pattern etc. when viewed through polarized sunglasses from any direction. The display quality is significantly improved as compared with the case where a conventional elliptically polarizing plate is used.

(2) By disposing a retardation plate below the upper polarizer of a TN liquid crystal display device in which the twist angle of liquid crystal molecules is 90 degrees, interference colors of the liquid crystal phase can be eliminated uniformly over a large screen. Display quality can be significantly improved.

(3) In an STN type liquid crystal display device in which the twist angle of liquid crystal molecules is 180 to 270 degrees, coloring occurs due to birefringence of the liquid crystal layer. The phase difference plate of the present invention is stuck between the upper polarizing plate or lower polarizing plate and the liquid crystal cell of the STN liquid crystal display device so that the optical axis thereof is in the range of 30 to 60 degrees, preferably 40 to 50 degrees. By matching, the display quality becomes good. By arranging the optical axes of the pair of polarizing plates in an orthogonal or nearly orthogonal state, or in a parallel or nearly parallel state, black-and-white display is possible, and display quality is improved.

〔Example〕

Hereinafter, the present invention will be described with reference to examples. The present invention is not limited to these. In the examples, the retardation value of the retardation plate was measured using a Senarmon compensator (546 nm) provided for a polarizing microscope, and a halogen lamp was used as a light source. The linear polarizing plate in the examples is one obtained by uniaxially adsorbing iodine as a dichroic dye on polyvinyl alcohol, prepared by a method described in, for example, JP-A-61-20003. If necessary, a transparent non-rotatory polymer film such as cellulose diacetate is bonded as a protective film.

Example 1 As a raw film, a thickness of 180 μm, Δx was 12 μm,
The rate of change in thickness (G ') was a 1.5 μm / cm transparent transparent polycarbonate film (135 ° C.).

First, a sample of a JIS No. 3 dampen (5 mm width) was taken from the raw film and subjected to a tensile test at a temperature near the heating deformation temperature, and the temperature at which the apparent yield point disappeared in the stress-strain curve was about
It was required to be 165 ° C. (The stress-strain curve is shown in Fig. 1.) Stretching is performed by Hirano Metal Co., Ltd. tenter equipment (2m width x
(9 m length) by horizontal uniaxial stretching.

The raw film is heated to 190 ° C. in the preheating step, and the birefringence of the raw film is set to 0.4 × 10 ⁻⁴ , and then 170 ° C. in the stretching step.
The film was uniaxially stretched 1.8 times in the horizontal direction and heat-treated at 140 ° C. to obtain a stretched film having a thickness of about 100 μm. The stretched film was 540 nm, ΔR was 4.5%, G was 0.57% / cm, and was a homogeneous retardation plate with little optical unevenness.

This retardation plate is attached to one surface of the polarizing plate using an acrylic adhesive so that the optical axis is about 45 degrees,
The composite polarizing plate of the present invention was obtained.

Furthermore, when this retardation plate is used by gluing it between the liquid crystal cell of a liquid crystal display device with a liquid crystal molecule twist angle of 200 degrees and the upper polarizer, the background color is white and the display part is almost black and white. As a result, there was no color unevenness such as a rainbow pattern, and a liquid crystal display device having good display quality was obtained.

Example 2 Using the raw film of Example 1 and a tenter, horizontal uniaxial stretching was performed. After heating the raw film to 195 ° C. in the preheating step and setting the birefringence of the raw film to 0.24 × 10 ⁻⁴ ,
In the stretching process, perform 1.5 times stretching uniaxially at 175 ° C 140
A heat treatment was performed at a temperature of 100 ° C. to obtain a stretched film having a thickness of 120 μm.

The stretched film has 280 nm, ΔR of 3.5%, and G of 0.48
% / Cm was a homogeneous retardation plate with little optical unevenness.

This retardation plate was adhered to one surface of the polarizing plate using an acrylic pressure-sensitive adhesive so that the optical axis was about 45 degrees, to obtain a composite polarizing plate of the present invention.

Furthermore, when this retardation plate was bonded and used between a liquid crystal cell of a liquid crystal display device having a liquid crystal molecule twist angle of 200 degrees and an upper polarizing plate via an adhesive, the background color was white and the display portion was black. Almost black and white display became possible, and there was no color unevenness such as a rainbow pattern, and a liquid crystal display device with good display quality was obtained.

Example 3 Using the raw film of Example 1 and a tenter, horizontal uniaxial stretching was performed. After heating the raw film to 193 ° C. in the preheating step and setting the birefringence of the raw film to 0.35 × 10 ⁻⁴ ,
In the stretching process, stretch 2.2 times horizontally uniaxially at 168 ° C.
Heat treatment was performed at 0 ° C. to obtain a stretched film having a thickness of about 82 μm. The stretched film has 830 nm, ΔR is 6.6%, G
Is a 0.76% / cm homogeneous retardation plate with little optical non-uniformity. The retardation plate is pasted between the liquid crystal cell of the liquid crystal display device whose liquid crystal molecules have a twist angle of 200 degrees and the upper polarizer with an adhesive. When used in combination, a substantially black-and-white display with a white background and a black display portion was possible, and there was no color unevenness such as a rainbow pattern, and a liquid crystal display device with good display quality was obtained.

Comparative Example 1 Thickness (x) 180 μm, Δx is 26 μ as a raw film
m and G 'were carried out in exactly the same manner as in Example 1 except that a transparent polycarbonate film of 3.8 μm / cm (heat deformation temperature: 135 ° C.) was used to obtain a stretched film having a thickness of 100 μm.
The stretched film was 535 nm, ΔR was 11.4%, and G was 1.45.
% / Cm, the optical unevenness was large, and only a retardation plate having poor homogeneity as compared with Example 1 was obtained.

Comparative Example 2 In Example 1, in the stretching step, the film was uniaxially stretched 1.8 times at 153 ° C. and heat-treated at 140 ° C. to obtain a stretched film having a thickness of 100 μm. The stretched film has a thickness of 1010 nm and a ΔR
10%, G is 1.4% / cm and optical unevenness is large.
Only a retardation plate inferior in homogeneity was obtained.

Comparative Example 3 Using exactly the same raw material as in Example 1, after preheating at a temperature of 170 ° C., the film was stretched uniaxially longitudinally between rolls having different peripheral speeds to a thickness of about 95 μm (neck-in rate 13
%). The stretched film is 670n
m, ΔR was 12.5%, and G was 1.60% / cm, and the optical unevenness was large and only a retardation plate having poor homogeneity as compared with Example 1 was obtained.

Example 4 Thickness (x) 180 μm and Δx 16 μm as a raw film
m and G 'were carried out in exactly the same manner as in Example 1 except that a transparent polycarbonate film of 2.2 μm / cm (heating deformation temperature: 135 ° C.) was used, and a stretched film having a thickness of 100 μm was obtained. The stretched film has 545 nm, ΔR is 7.6%, and G is
At 0.98% / cm, it was a homogeneous retardation plate with little optical unevenness. This retardation plate was adhered to one surface of the polarizing plate using an acrylic pressure-sensitive adhesive so that the optical axis was about 45 degrees, to obtain a composite polarizing plate of the present invention. Further, when this retardation plate was applied to a liquid crystal display device in the same manner as in Example 1, a liquid crystal display device of good quality of substantially black and white display was obtained.

Example 5 As a raw film, the thickness (x) was 180 μm and Δx was 14
For μm and G ′, a transparent transparent polycarbonate film (heat deformation temperature: 132 ° C.) of 2.0 μm / cm was used, and the temperature at which the apparent yield point was not found in the stress-strain curve in the same manner as in Example 1 was about 160. ° C.

Stretching was performed by compression stretching using a pressure roll facility (diameter 260 mm, surface length 700 mm). The raw film is preheated to 150 ° C in a heating oven, and the birefringence of the raw film is set to 0.5 × 10 ^-4
After passing through the pressure rolls of 165 ℃,
Draws 60 times thick and 380 mm wide (neck-in rate 4
%). The stretched film is 890n
m, ΔR was 7.0%, and G was 0.65% / cm. This retardation plate was adhered to one surface of the polarizing plate using an acrylic pressure-sensitive adhesive so that the optical axis was about 45 degrees, to obtain a composite polarizing plate of the present invention. Furthermore, when this retardation plate was applied to a liquid crystal display device in the same manner as in Example 1, a liquid crystal display device of good quality of substantially black-and-white display was obtained.

Comparative Example 4 Using exactly the same raw material as in Example 5, the raw film was not preheated, but was passed through a pressure roll at 145 ° C. and stretched 1.3 times in one longitudinal axis (neck-in ratio: 3%). About 1
A 40 μm stretched film was obtained. The stretched film is 51
At 0 nm, ΔR was 14%, and G was 1.85% / cm, cracks due to stretching unevenness were observed, and only a retardation plate having large optical unevenness and inferior homogeneity as compared with Example 5 was obtained.

Example 6 As a raw film, thickness (x) was 400 μm and Δx was 26.
μm, G ′ is a 3.2 μm / cm polycarbonate copolymer film (PZTG6763, Eastman Chemical Co., heating deformation temperature: 81 ° C.), and the temperature at which the apparent yield point is eliminated by the same method as in Example 1. Was about 105 ° C.
After preheating the film at 135 ° C,
The film was subjected to transverse uniaxial stretching by a tenter method at a temperature of 22 ° C. to obtain a stretched film having a thickness of 240 μm. The stretched film was 485 nm, ΔR was 5.8%, G was 0.80% / cm, and was a homogeneous retardation plate with little optical unevenness. Using an acrylic adhesive, this retardation plate has an optical axis on one side of the polarizing plate.
The composite polarizing plate of the present invention was obtained by sticking at 45 degrees. Furthermore, when this retardation plate was applied to a liquid crystal display device in the same manner as in Example 1, a liquid crystal display device of good quality of substantially black-and-white display was obtained.

Comparative Example 5 In Example 6, the thickness (x) was 400 μm, and Δx was 45.
A stretched film was obtained in exactly the same manner as in Example 6, except that a raw film having μm and G ′ of 6 μm / cm was used. The stretched film is 525 nm, ΔR is 10.8%, and G is
At 1.41% / cm, the optical unevenness was so large that only a retardation plate having poor homogeneity as compared with Example 6 was obtained.

Example 7 As a raw film, the thickness (x) was 250 μm and Δx was 16
μm and G ′ are 3.5 μm / cm polyvinyl chloride film (Unroid VIPCHA150, Tsutsunaka Plastics Industry Co., Ltd.)
The temperature at which the apparent yield point disappeared was determined to be about 85 ° C. in the same manner as in Example 1. After preheating the film at a temperature of 120 ° C., the film was subjected to transverse uniaxial stretching by a tenter method at a temperature of 95 ° C. to obtain a stretched film having a thickness of 140 μm. The stretched film has a thickness of 310 nm,
R was 7.2% and G was 0.65% / cm, which was a homogeneous retardation plate with little optical unevenness. This retardation plate was attached to one surface of the polarizing plate using an acrylic pressure-sensitive adhesive so that the optical axis was about 45 degrees, to obtain a composite polarizing plate of the present invention. Further, when this retardation plate was applied to a liquid crystal display device in the same manner as in Example 2, a liquid crystal display device of good quality of substantially monochrome display was obtained.

Comparative Example 6 In Example 7, the thickness (x) was 250 μm, and Δx was 30.
A stretched film was obtained in exactly the same manner as in Example 7, except that a raw film having μm and G ′ of 4.3 μm / cm was used. The stretched film is 295 nm, ΔR is 12.3%, and G is
At 1.52% / cm, the optical unevenness was large, and only a retardation plate having poor homogeneity as compared with Example 7 was obtained.

Example 8 As a raw film, the thickness (x) was 200 μm and Δx was 15
Using a polysulfone film (heat deformation temperature: 174 ° C.) having μm and G ′ of 2.7 μm / cm, it was determined that the temperature at which the apparent yield point disappeared was about 200 ° C. in the same manner as in Example 1. . After preheating the film at a temperature of 230 ° C. in advance, it was subjected to transverse uniaxial stretching by a tenter method at a temperature of 210 ° C. to obtain a stretched film having a thickness of 105 μm. The stretched film was 780 nm, ΔR was 7.5%, G was 0.80% / cm, and was a homogeneous retardation plate with little optical unevenness. This retardation plate was attached to one surface of the polarizing plate using an acrylic pressure-sensitive adhesive so that the optical axis was about 45 degrees, to obtain a composite polarizing plate of the present invention. Further, when this retardation plate was applied to a liquid crystal display device in the same manner as in Example 3, a liquid crystal display device of good quality of substantially black-and-white display was obtained.

Comparative Example 7 In Example 8, the thickness (x) was 200 μm, and Δx was 27.
A stretched film was obtained in the same manner as in Example 1, except that a raw film having μm and G ′ of 4.0 μm / cm was used. The stretched film was 790 nm, ΔR was 12.6%, G was 1.61% /
In cm, optical unevenness was large and only a retardation plate having poor homogeneity as compared with Example 8 was obtained.

[Brief description of the drawings]

FIG. 1 shows stress-strain curves of the polycarbonate films used in Examples 1 to 8.

Continuation of the front page (56) References JP-A-63-189804 (JP, A) JP-A-56-130703 (JP, A) JP-B-8-30806 (JP, B2) (58) Fields investigated (Int) .Cl. ⁶ , DB name) G02B 5/30

Claims (5)

(57) [Claims] 1. A film or sheet formed by uniaxially stretching a thermoplastic polymer film or sheet, wherein the retardation value is in the range of 30 to 1200 μm and the amplitude of the retardation is 10% or less. And the rate of change is 1.3% / cm or less. 2. A thermoplastic polymer film or sheet having a thickness (x) fluctuation of 0.1x or less and a change rate of 0.015x / cm or less as said thermoplastic polymer film or sheet. The phase difference plate according to claim 1, wherein: 3. A bonded polarizing plate obtained by laminating the retardation plate according to claim 1 on a polarizing plate. 4. A swing width of the thickness (x) is 0.1x or less, and
The method for producing a retardation plate according to claim 1, wherein a thermoplastic polymer film or sheet having a rate of change of 0.015x / cm or less is uniaxially stretched. 5. The method according to claim 4, wherein the stretching temperature is equal to or higher than a temperature at which an apparent yield point disappears in a stress-strain curve in a tensile test of the thermoplastic polymer.